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Thread: Major teardown for 915is engines.

  1. #1
    Senior Member Kitfox Pilot's Avatar
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    Default Major teardown for 915is engines.

    https://legacy.rotaxowner.com/si_tb_...b-915i-011.pdf

    https://legacy.rotaxowner.com/si_tb_...915i-011is.pdf



    Looks like a full cylinder removal will be required. Seral numbers start just after mine was built. Lucked out there but check yours out.
    Harlan and Susan Payne
    Sold Piper Archer
    Flying FarmFox STI Kitfox N61HP
    Rotax 915is, Airmaster prop
    https://www.youtube.com/channel/UC5A...oCVUP15G0uB-Yw

  2. #2
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    Default Re: Major teardown for 915is engines.

    Ouch. Looks like all the cylinders have to come off but you don't have to split the case (assuming you don't drop a T40 bit in there).
    Kitfox 5 (under construction)
    Commercial SE/ME, CFII

  3. #3
    Senior Member Kitfox Pilot's Avatar
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    Default Re: Major teardown for 915is engines.

    haha, I have dropped things before..
    Harlan and Susan Payne
    Sold Piper Archer
    Flying FarmFox STI Kitfox N61HP
    Rotax 915is, Airmaster prop
    https://www.youtube.com/channel/UC5A...oCVUP15G0uB-Yw

  4. #4
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    Default Re: Major teardown for 915is engines.

    Quote Originally Posted by Kitfox Pilot View Post
    haha, I have dropped things before..
    I'm a bit of a gear head so forgive this side trip. About six years ago I bought my first Porsche. At my first oil change I found metal in the filter. When I bought the car I didn't know of a flaw which affected about 10 percent of the cars (Boxsters, Caymans and 911s) with the M96 engine, where a ball bearing could fail - often catastrophically. While I found my issue very early there had still been metal pumping through the entire engine so the only solution was a 100% tear down.

    I'll save you all those boring details just to get to the point. The M96 engine is assembled in the weirdest possible way. The case is split down the middle like an aircraft engine, but the cylinders are part of the crank case and you slap the heads on top of that. You start with the crankshaft with all the connecting rods, but only the pistons for the left half of the engine. Those are bolted into a massive steel cage called the bearing carrier (it also contains those oil squirter nozzles which are the subject of this 915 service bulletin). That assembly is installed into the left half of the crank case.
    Screenshot 2021-12-02 at 10-29-12 Photobucket 0217150916_zpsmbqsebb3 jpg.png
    Screenshot 2021-12-02 at 10-28-44 Photobucket 0217150916a_zps8abedvcd jpg.png
    Next, you install the right half of the crankcase but there's no way to have the pistons installed when you do this. Installing those pistons is akin to building a ship inside a bottle (hoping at least some of you are old enough to know what that means). You rotate the crankshaft so the front connecting rod is visible in the cylinder bore. There is a hole starting at the back of the engine which goes all the way to that cylinder. You then use a special tool to install the wrist pin through the rear cylinder, through the middle cylinder and into the piston/wrist pin until it butts up against the wrist pin clip which you hopefully remembered to install before sliding the piston in.

    Now you have to install the aft wrist pin clip through that same passage. There's another special tool used for that and it involves a solid love tap to seat the wrist pin. Many people choke at this point and either think they have it installed but it launches out during the first engine run, or it goes "ping!" and flies down inside the engine. And if that's not enough stress you get to do it again on the middle and rear cylinders. Terrified at the thought of losing a wrist pin clip I put on my tool designer hat and created a tool which would slide inside the wrist pin and operate on the same principal as a chinese finger puzzle. It allowed me to give that wrist pin a tug to make sure everything was seated, and if not it would prevent the wrist pin clip from being lost inside the engine.
    Screenshot 2021-12-02 at 10-29-42 Photobucket 0228151028a_zpsjxskxuj4 jpg.png
    Screenshot 2021-12-02 at 10-29-50 Photobucket 0301151020a_zpsgluh5qhp jpg.png
    Happy to say it worked perfectly. I put 10k more miles on that car before selling it to buy my Citabria.
    Screenshot 2021-12-02 at 10-27-42 Photobucket 03221519122_zps0lu3oxjl jpg.png
    Kitfox 5 (under construction)
    Commercial SE/ME, CFII

  5. #5
    Senior Member Kitfox Pilot's Avatar
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    Default Re: Major teardown for 915is engines.

    That's quite an engine to rebuild right there in your pics. I can hear that snap ring ping as I looked at it. Haha
    Harlan and Susan Payne
    Sold Piper Archer
    Flying FarmFox STI Kitfox N61HP
    Rotax 915is, Airmaster prop
    https://www.youtube.com/channel/UC5A...oCVUP15G0uB-Yw

  6. #6
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    Default Re: Major teardown for 915is engines.

    Looks like my engine is before that lot of numbers too. Maybe they had the anniversary engines built by someone else?
    Starfox

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